For many years, atmospheric pollution has significantly increased, and became a worldwide environmental problem which has negative impacts on human health and well-being.
It is the outermost tissues like skin, hair, nails and lungs that are initially and directly exposed to harmful pollutants. Thus, the skin is exposed on a daily basis to environmental pollution such as volatile organic compounds, cigarette smoke, ozone, and particulate matter.
Atmospheric pollution is composed of various types of chemical, xenobiotic products and particles. Three major categories of pollutants which may exert harmful effects on exposed tissues are gases, heavy metals and particulates elements.
Atmospheric pollutants can be found both outside, for example due to diesel motor particles, ozone, or heavy metals, and at home, where pollution may be due in particular to solvents released by paints, glues or wallpapers such as toluene, styrene, xylene, benzaldehyde or cigarette smoke.
Among air pollutants, ozone and particle pollution are the most widespread air pollutants and among the most dangerous.
At the ground level, ozone (O3) is formed by the interaction of sunlight on primary pollutants as nitrogen oxides and volatile organic compounds, particularly motor vehicle exhaust emissions.
As ozone is a small molecule and an extremely reactive oxidant, it reacts quickly with the outermost human tissues, noticeably with the respiratory tract and the skin.
More particularly, ozone has been found to lead to toxicological damages (Afaq F. et al. J Invest Dermatol, 2009: 129: 2396-2403.) and to increase DNA damages in normal human epidermal keratinocytes, that will ultimately impair normal cellular function (James T. McCarthy et al. Exp Dermatol, 2013, 22, 358-379).
Repetitive and prolonged exposure to atmospheric pollution acts synergistically with UV exposure to exert negative consequences on skin. This potentially can lead to irritation, inflammation and to increase photodamage and skin aging (Carletto, C. et al. Int J Cosmet Sci. 2000 October; 22(5):361-70).
Otherwise, it is well known that free radicals play a key role in the aging and photo-aging process, and more particularly in the formation of oxidized, damaged proteins (Harman et al. J. Gerontol., 1956, 11(3), 298-300).
Such external aggressions of the skin by atmospheric pollution can lead to a slow, progressive process of aging which affects all the cutaneous layers of skin and cumulates with chronological aging. The appearance of the skin is modified and one can observed the apparition of wrinkles and fine lines, hyper or hypo-pigmentation blemishes, dryness or even dehydration of the skin, thinning of the epidermis, elastosis, imperfections, age spots. All of these changes affect not only the skin, but also the nails and the hair. These modifications are due, in particular, to a decrease in the functions of cell renewal, and extracellular matrix molecule synthesis, such as collagen, elastin and hyaluronic acid.
Recent avenues of research have been explored to identify active agents capable of fighting environmental stresses (sun, pollution, etc.). These researches have led to the disclosure of numerous more or less effective active agents. As an example, patent application US20070003536 disclosed a method for protecting skin against oxidizing species and oxidative damages of the skin. The method includes applying an admixture of more than ten ingredients selected to combat effects of reactive oxygen and nitrogen species, such as ascorbic acid, SOD, glutathione, grape component, green tea, flavonoid, grapeseed component, green tea component, tocopherol, etc. . . . .
Otherwise, patent application US2002/0192178 disclosed a method for protecting skin against the effects of pollution, comprising applying to the skin a composition comprising an aqueous extract of maize. Patents FR 2915380 and FR 2915383 disclosed a rice peptide extract intended to protect skin from oxidative damages.
However a high demand for cosmetic treatment that protects skin against adverse effects of pollution currently exists. Therefore, it remains important to identify new compounds capable of preventing or protecting skin from atmospheric pollution and improving skin regeneration.